Characterization of Triple Porosity System in a Carbonate Reservoir Utilizing Image Log and Conventional Well Logs

Vugs and fractures widely develop in the carbonate reservoirs. Existence of these porosities in addition to matrix porosity leads a complex triple porosity system in the carbonate reservoirs. Accurate understanding of porosity system is vital in reservoir simulation and petrophysical evaluation of heterogeneous carbonates. Image logs are high resolution un-conventional logs which provide a pseudo azimuthal picture from borehole wall. Fractures and vugs can be separated from matrix in image log by utilizing image processing techniques. After recognition of vugs and fractures، the amount of each one can be determined. By integrating conventional logs and FMI (Fullbore Formation Micro Imager) (a type of image logs) a triple porosity reservoir can be quantitatively characterized. We applied aforementioned method to Sarvak reservoir formation in an oilfield in SW of Iran، to characterize its porosity system. The results verified by manually detected fractures in the FMI and also secondary porosity calculated by wire line logs. Comparison of porosity logs derived by means of proposed method with FMI›s fracture density logs shows that except in highly shaly carbonate layers، which this method ignore all vuggy porosity، the proposed method works well and the result can be employed for further petrophysical and reservoir simulation purposes.